The present invention relates to a thin switch including a domed contact, which is used as a signal switch in portable electronic devices such as a movable telephone.
The signal switch mounted on a surface of a portable electronic device primarily requires thinness. FIG. 12(A) and FIG. 12(B) illustrate a thin switch having a domed contact, which is typically used on a surface of a portable electronic device.
This thin switch comprises, housing 1 made from a resin, coupling terminals 2 and 3 mounted to the housing for coupling the thin switch to an outer circuit, outer fixed ring-shape contact 4 mounted on the bottom of the housing, center fixed disc-shape contact 5 mounted at the center of the outer fixed ring-shape contact 4, domed movable contact 6 made of an elastic thin-metal-plate, which is mounted so that the circumference always contacts the outer fixed contact 4, and insulating film 7 covering an open surface of housing 1. Terminal 2 and outer fixed contact 4 are a unitary structure made from a metal sheet. Terminal 3 and center fixed contact 5 are also a unitary structure made from a metal sheet. These unitary forms are fixed to housing 1 through an insertion molding process.
When the center part of insulation film 7 is pressed, a tip of movable contact 6 is lowered to touch center fixed contact 5, which makes fixed contact 4 and center fixed contact 5 electrically conductive, in other words, terminal 2 and terminal 3 become conductive. When the pressing force is removed, movable contact 6, because of its elastic properties restores itself to an initial dome form, which terminates the conduction between terminal 2 and terminal 3.
Recently, portable electronic devices require reduced size and cost, which places the same requirement on the thin switch mounted on the surface of the portable electronic device, namely the thin switch must be thinner and be available at a lower cost. However, since a conventional thin switch is made by an insert-molding method, it is difficult to meet this requirement. A certain thickness is necessary for filling up a mold with sufficient resin, which prevents the thin switch from becoming thinner than a certain limit. For instance, a square switch of 5 mm side length cannot be thinner than 0.8 mm in thickness.
Furthermore, a mold used in the insert-molding method has a complicated structure and is expensive. Molding equipment is also expensive. Accordingly, it is difficult for the thin switch producer to lower the manufacturing cost.
The present invention provides a thin switch which overcomes these problems.